Controlling light source wavelengths for selectable phase shifts between pixels in digital lithography systems

ABSTRACT

A digital lithography system may adjust a wavelength of the light source to compensate for tilt errors in micromirrors while maintaining a perpendicular direction for the reflected light. Adjacent pixels may have a phase shift that is determined by an optical path difference between their respective light beams. This phase shift may be preselected to be any value by generating a corresponding wavelength at the light source based on the optical path difference. To generate a specific wavelength corresponding to the desired phase shift, the light source may produce multiple light components that have wavelengths that bracket the wavelength of the selected phase shift. The intensities of these components may then be controlled individually to produce an effect that approximates the selected phase shift on the substrate.

TECHNICAL FIELD

This disclosure generally describes a method of generating a preselectedphase shift between pixels in a digital lithography system. Morespecifically, this disclosure describes controlling a wavelength outputof a light source to generate or approximate an effect of thepreselected phase shift on a substrate during a lithography process.

BACKGROUND

Spatial light modulators are often used to impose a spatial varyingmodulation on a beam of light. Digital micromirror devices (DMDs), whichare an example of spatial light modulators, are used as reflectivedigital light switches in a variety of applications, including digitallithography. For digital lithography, the DMD is generally combined withother image processing components, such as memory, a light source andoptics, and used to project the desired pattern onto a photosensitivematerial on the substrate being processed.

A DMD generally includes several hundred thousand microscopic mirrors(“micromirrors”) arranged in a rectangular array. Each micromirrorcorresponds to a single pixel of the image to be displayed and can betilted at various angles about a hinge. Depending on the tilt angle ofthe micromirror, the micromirror is in an “on” or “off” state. In the onstate, light is reflected from the DMD into a lens and ultimately apixel is brightly projected onto a substrate. In the off state, light isdirected elsewhere, such as a light dump, and the projected pixelappears dark.

The phase shift between adjacent micromirrors of the DMD affects theresolution of the projected image and the depth of focus. Generally, thephase shift between adjacent micromirrors of the DMD is 0 degrees. A DMDhaving the 0 degree phase shift between adjacent micromirrors is knownas a blazed DMD. While blazed DMDs exhibit good resolution and depth offocus, as device dimensions become smaller, improved resolution andbetter depth of focus are needed, especially for line spacing. Inmask-based lithography, hard phase shift masks have been used to printvery narrow and dark lines. However, hard phase shift masks are limitedby the topology of the design.

Thus, there is a need in the art for an improved spatial lightmodulator, which increases image resolution and depth of focus, anddigital lithography methods for use thereof.

SUMMARY

In some embodiments, a digital lithography system may include a firstspatial light modulator pixel configured to direct a first light beamonto a substrate during a digital lithography process; a second spatiallight modulator pixel configured to direct a second light beam onto thesubstrate during the digital lithography process; a light sourceconfigured to generate the first light beam. The first light beam mayinclude a plurality of components including a first component having afirst wavelength that generates a first phase shift that is greater thana preselected phase shift; and a second component having a secondwavelength that generates a second phase shift that is less than thepreselected phase shift. The digital lithography system may include acontroller configured to control intensities of the plurality ofcomponents to generate an effect on the substrate that approximates thepreselected phase shift.

In some embodiments, a method of adjusting a phase shift between pixelsin digital lithography systems may include projecting a first light beamonto a first spatial light modulator pixel. The first spatial lightmodulator pixel may direct the first light beam onto a substrate duringa digital lithography process. The first light beam may include aplurality of components including a first component having a firstwavelength that generates a first phase shift that is greater than apreselected phase shift; and a second component having a secondwavelength that generates a second phase shift that is less than thepreselected phase shift. The method may also include projecting a secondlight beam onto a second spatial light modulator pixel. The secondspatial light modulator pixel may direct the second light beam onto thesubstrate during the digital lithography process. The method may alsoinclude controlling intensities of the plurality of components togenerate an effect on the substrate that approximates the preselectedphase shift.

In some embodiments, a method of adjusting or selecting a phase shiftbetween pixels in digital lithography systems may include projecting afirst light beam onto a first spatial light modulator pixel. The firstspatial light modulator pixel may direct the first light beam onto asubstrate during a digital lithography process. The method may alsoinclude projecting a second light beam onto a second spatial lightmodulator pixel. The second spatial light modulator pixel may direct thesecond light beam onto the substrate during the digital lithographyprocess. The second spatial light modulator pixel may be adjacent to thefirst spatial light modulator pixel in an array of spatial lightmodulator pixels. The method may additionally include controlling awavelength of the first light beam and/or a wavelength of the secondlight beam based on an optical path difference between the first lightbeam and the second light beam to produce a preselected phase shiftbetween the first light beam and the second light beam on the substrate.

In any embodiments, any and all of the following features may beimplemented in any combination and without limitation. The secondspatial light modulator pixel may be adjacent to the first spatial lightmodulator pixel in an array of spatial light modulator pixels in adigital micromirror device. The first spatial light modulator pixel mayinclude a micromirror that adjusts between an on position that reflectslight onto the substrate and an off position that reflects light awayfrom the substrate. The light source may also be configured to generatethe second light beam, such that the first light beam and the secondlight beam originate from the light source. The second light beam may begenerated from a different light source, and the controller may befurther configured to control intensities of components in the secondlight beam to correct for a tilt error in the second spatial lightmodulator pixel that is different from a tilt error in the first spatiallight modulator pixel. The light source may include a plurality ofgroups of laser diodes. A first subset of the plurality of groups oflaser diodes may be configured to output approximately the firstwavelength, and a second subset of the plurality of groups of laserdiodes may be configured to output approximately the second wavelength.The light source may include a homogenizing rod that mixes the firstcomponent together with the second component to generate a uniform firstlight beam. The plurality of components may include a plurality ofadditional components in addition to the first component and the secondcomponent. The first wavelength may generate a first phase shift that isapproximately 20° greater than the preselected phase shift. The secondwavelength may generate a second phase shift that is approximately 10°less than the preselected phase shift. The preselected phase shift maybe selectable to be any phase shift between 0° and 359°. Controlling theintensities of the plurality of components may include calculatingweights for each of the plurality of components in a linear combinationof the deviations between the first phase shift and the second phaseshift from the preselected phase shift such that the linear combinationis approximately zero. The weights in the linear combination maycorrespond to the intensities of the plurality of components.Approximating the preselected phase shift may generate a pattern oflight intensity on the substrate that approximates a pattern of lightintensity that would be present on the substrate using a singlewavelength corresponding to the preselected phase shift. The first phaseshift may be calculated from the first wavelength and an optical pathdifference between the first light beam on the second light beam. Thesecond spatial light modulator pixel may be adjacent to the firstspatial light modulator pixel in an array of spatial light modulatorpixels in a digital micromirror device, and the second light beam mayalso include the first component and the second component. Controllingthe wavelength of the first light beam may include switching betweendifferent laser diodes that generate light having different wavelengths.Controlling the wavelength of the first light beam may include changingthe wavelength of the first light beam by controlling a temperature of alight source, mechanically altering a cavity of the light source, orelectro-acoustically altering the cavity of the light source.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of variousembodiments may be realized by reference to the remaining portions ofthe specification and the drawings, wherein like reference numerals areused throughout the several drawings to refer to similar components. Insome instances, a sub-label is associated with a reference numeral todenote one of multiple similar components. When reference is made to areference numeral without specification to an existing sub-label, it isintended to refer to all such multiple similar components.

FIG. 1 is a perspective view of a system for digital lithography,according to some embodiments.

FIG. 2 illustrates a perspective schematic view of an image projectionsystem of the system, according to some embodiments.

FIG. 3 illustrates a digital micromirror device (DMD), according to someembodiments.

FIG. 4A illustrates a pair of adjacent micromirrors directing lightbeams towards a substrate, according to some embodiments.

FIG. 4B illustrates adjacent micromirrors where the tilt angle isdifferent from an ideal tilt angle, according to some embodiments.

FIG. 4C illustrates how variations in the tilt angles may be addressedby changing the angle of the light beams, according to some embodiments.

FIG. 5 illustrates how an optical path difference (OPD) between twoadjacent micromirrors may result in a phase shift on the substrate,according to some embodiments.

FIG. 6 illustrates a system for adjusting a phase shift between pixelsin digital lithography system, according to some embodiments.

FIG. 7 illustrates a flowchart of a method for adjusting or selecting aphase shift between pixels in digital lithography systems, according tosome embodiments.

FIG. 8 illustrates a light source that may be used in lithographysystems, according to some embodiments.

FIG. 9 illustrates a system for using light beams having multiplewavelengths that bracket a preselected wavelength, according to someembodiments.

FIG. 10 illustrates a graph of the effect of using a light beam withmultiple light components that bracket the preselected phase shift,according to some embodiments.

FIG. 11 illustrates graphs that show how multiple components can be usedto approximate and tune any preselected wavelength, according to someembodiments.

FIG. 12 illustrates a flowchart of a method of selecting or adjusting aphase shift between pixels in digital lithography systems, according tosome embodiments.

FIG. 13 illustrates an exemplary computer system, in which variousembodiments may be implemented.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of a system 100 for digital lithography,according to some embodiments. The system 100 may include a base frame110, a slab 120, one or more stages 130 (two are shown as an example),and/or a processing apparatus 160. The base frame 110 may rest on thefloor of a fabrication facility and support the slab 120. Passive airisolators 112 may be positioned between the base frame 110 and the slab120. In some embodiments, the slab 120 may include a monolithic piece ofgranite, and the one or more stages 130 may be disposed on the slab 120.A substrate 140 may be supported by each of the one or more stages 130.A plurality of holes (not shown) may be formed in the one or more stages130 for allowing a plurality of lift pins (not shown) to extendtherethrough. The lift pins may rise to an extended position to receivethe substrate 140, such as from one or more transfer robots (not shown).The one or more transfer robots may be used to load and unload asubstrate 140 from the one or more stages 130.

The substrate 140 may be, for example, made of glass and used as part ofa flat panel display. In some embodiments, the substrate 140 may be madeof other materials. In some embodiments, the substrate 140 may have aphotoresist layer formed thereon. A photoresist may be sensitive toradiation and may include a positive photoresist or a negativephotoresist, meaning that portions of the photoresist exposed toradiation may be respectively soluble or insoluble to a photoresistdeveloper applied to the photoresist after a pattern is written into thephotoresist. The chemical composition of the photoresist may determinewhether the photoresist will be a positive photoresist or negativephotoresist. For example, the photoresist may include at least one ofdiazonaphthoquinone, a phenol formaldehyde resin, poly(methylmethacrylate), poly(methyl glutarimide), and/or SU-8. In this manner,the pattern may be created on a surface of the substrate 140 to form theelectronic circuitry.

The system 100 may further include a pair of supports 122 and a pair oftracks 124. The pair of supports 122 may be disposed on the slab 120,and the slab 120 and the pair of supports 122 may be formed as a singlepiece of material. The pair of tracks 124 may be supported by the pairof the supports 122, and the one or more stages 130 may be movable alongthe tracks 124 in the X-direction. In some embodiments, the pair oftracks 124 may include a pair of parallel magnetic channels. As shown,each track 124 of the pair of tracks 124 may be linear. In someembodiments, the track 124 may have a non-linear shape. An encoder 126may be coupled to each of the one or more stages 130 in order to providelocation information to a controller (not shown).

The processing apparatus 160 may include a support 162 and/or aprocessing unit 164. The support 162 may be disposed on the slab 120 andmay include an opening 166 for the one or more stages 130 to pass underthe processing unit 164. The processing unit 164 may be supported by thesupport 162. In some embodiments, the processing unit 164 my include apattern generator configured to expose a photoresist in aphotolithography process. In some embodiments, the pattern generator maybe configured to perform a maskless lithography process. The processingunit 164 may include a plurality of image projection apparatuses (asshown in FIG. 2 ). In some embodiments, the processing unit 164 mayinclude multiple light sources, such as laser diodes. Each imageprojection apparatus may be disposed in a case 165. The processingapparatus 160 may be used to perform mask-less direct patterning.

During operation, one of the one or more stages 130 may move in theX-direction from a loading position, as shown in FIG. 1 , to aprocessing position. The processing position may refer to one or morepositions of the stage 130 as the stage 130 passes under the processingunit 164. During operation, the one or more stages 130 may be lifted bya plurality of air bearings (not shown) that may be movable along thepair of tracks 124 from the loading position to the processing position.A plurality of vertical guide air bearings (not shown) may be coupled toeach of the one or more stages 130 and positioned adjacent an inner wall128 of each support 122 in order to stabilize the movement of the stage130. Each of the one or more stages 130 may also be movable in theY-direction by moving along a track 150 for processing and/or indexingthe substrate 140. Each of the one or more stages 130 may be capable ofindependent operation and may scan a substrate 140 in one direction andstep in the other direction. In some embodiments when one of the one ormore stages 130 may be scanning a substrate 140, another of the one ormore stages 130 may be unloading an exposed substrate and loading thenext substrate to be exposed.

A metrology system may measure the X and Y lateral position coordinatesof each of the one or more stages 130 in real time so that each of theplurality of image projection apparatuses can accurately locate thepatterns being written in a photoresist covered substrate. The metrologysystem may also provide a real-time measurement of the angular positionof each of the one or more stages 130 about the vertical or Z-axis. Theangular position measurement may be used to hold the angular positionconstant during scanning by means of a servo mechanism, or it can beused to apply corrections to the positions of the patterns being writtenon the substrate 140 by the image projection apparatus 290 as shownbelow in FIG. 2 . These techniques may be used in any combination andwithout limitation.

FIG. 2 illustrates a perspective schematic view of an image projectionsystem 270 of the system 100, according to some embodiments. An imageprojection system may include a spatial light modulator, a focus sensorand/or camera, and a projection lens. As shown in FIG. 2 , the imageprojection system 270 may include a light source 272, an aperture 274, alens 276, a frustrated prism assembly 288, one or more digitalmicromirror devices (DMDs) 280 (one is shown), a light dump 282, a focussensor and camera 284, and/or a projection lens 286. The frustratedprism assembly 288, the DMD 280, the focus sensor and camera 284, andthe projection lens 286 may be part of an image projection apparatus290. In some embodiments, the light source 272 may include a lightemitting diode (LED) or a laser, and the light source 272 may be capableof producing a light having predetermined or adjustable wavelength. Forexample, the predetermined wavelength may be in the blue or nearultraviolet (UV) range, such as less than about 450 nm. The frustratedprism assembly 288 may include a plurality of reflective surfaces. Inone embodiment, the projection lens 286 may include a 6× or a 10×objective lens. Other embodiments of an image projection system, whichmay include a spatial light modulator other than one or more DMDs, mayinclude fewer or more components, as necessary in the system for thatparticular spatial light modulator.

This disclosure may refer to DMDs as an example of a spatial lightmodulator. However, other spatial light modulators are also contemplatedin the present disclosure. Other spatial light modulators may include,but are not limited to, arrays of liquid crystals, such as liquidcrystal displays (LCDs) and ferroelectric liquid crystal displays(FLCoS), and arrays of microscopic light emitting devices (microLEDs).Each spatial light modulator may include an array of spatial lightmodulator pixels that are switchable between “on” and “off” such thatthe pattern of spatial light modulator pixels may modulate the opticalbeam to provide the selected level of attenuation. In operation, thespatial light modulator pixels may be controllable such that each pixelis bright, dark and/or attenuated.

During operation of the image projection system 270 shown in FIG. 2 , alight beam 273 having a predetermined or adjustable wavelength, such asa wavelength in the blue range, may be produced by the light source 272.The light beam 273 may be reflected to the DMD 280 by the frustratedprism assembly 288. As shown in FIG. 3 , a DMD may include a pluralityof micromirrors, and the number of micromirrors may correspond to thenumber of pixels to be projected. The plurality of micromirrors may beindividually controllable, and each micromirror of the plurality ofmicromirrors may be at an on position or off position, based on the maskdata provided to the DMD 280 by the controller (not shown). When thelight beam 273 reaches the micromirrors of the DMD 280, the micromirrorsthat are in the on position may reflect the light beam 273, i.e.,forming the plurality of write beams, to the projection lens 286. Theprojection lens 286 may then project the write beams to the surface ofthe substrate 140. The micromirrors that are in the off position mayreflect the light beam 273 to the light dump 282 or another locationinstead of the surface of the substrate 140.

FIG. 3 illustrates a DMD 380, according to some embodiments. The DMD 380may be used in the image projection apparatus 290 and the system 100described above. The DMD 380 may also be useful in any other system ordevice utilizing a DMD. The DMD 380 may include a plurality of spatiallight modulator pixels, which are shown as micromirrors 381, arranged ina micromirror array 383. The DMD 380 may be used as a spatial lightmodulator, and the micromirrors 381 may be tilted at various degrees andused to adjust the reflected angle of the illumination beam on the DMD380 so that after reflection the on beam is aimed down the center of theimage projection apparatus 290 and the image created in the illuminationsystem is centered in the projection system. In one example, the stableposition for each micromirror 381 may be plus or minus about 12 degreeswith an error of approximately +1.0 degree with respect to the surfaceof the micromirror 381. For example, a first tilt position 389 maycorrespond to plus 12±1.0 degrees and a second tilt position 391 maycorrespond to minus 12.0±1.0 degrees.

The edges 385 of micromirrors 381 may be arranged along orthogonal axes,such as the X axis and the Y axis. These axes may be congruent withsimilar axis referenced to the substrate 140 or a stage coordinatesystem after taking into account a 90 degree fold introduced by thefrustrated prism assembly 288. However, hinges 387 on the micromirrors381 may be located on opposing corners of the micromirrors 381 causingthem to pivot on axis at 45 degrees to the X axis and Y axis. Asdiscussed above, these micromirrors 381 may be switched between on andoff positions by varying the angle of tilt of the micromirrors.

In some embodiments, the hinges 387 may be diagonally oriented to tilteach of the micromirrors 381 on an axis at 45 degrees to an X axis and aY axis of each of the micromirrors 381. In other embodiments, the hinges387 may be oriented parallel to an edge 385 of each of the micromirrors381 to tilt each of the micromirrors 381 on an axis parallel to the edge385 of each of the micromirrors 381. In one example, all of the hinges387 may be diagonally oriented. In another example, all of the hinges387 may be oriented parallel to an edge 385 of each of the micromirrors381. In yet another example, a first portion of the hinges 387 may bediagonally oriented and a second portion of the hinges 387 may beoriented parallel to an edge 385 of each of the micromirrors 381.

In conventional, blazed DMDs, the phase shift between adjacentmicromirrors may be 0 degrees. The conventional 0-degree phase shift mayresult in very little cancellation. However, the phase shift betweenadjacent micromirrors 381 of the DMD 380, for example first micromirror381 a and second micromirror 381 b, may be equal to or about 180degrees. This configuration is referred to as an anti-blazed DMD. Whenthe phase shift between adjacent spatial light modulator pixels, forexample the first micromirror 381 a and the second micromirror 381 b, is180 degrees, there is exact or nearly exact cancellation between theadjacent micromirrors 381 and there is symmetric brightening betweenadjacent pixels. In one example, each pair of adjacent micromirrors 381has a 180-degree phase shift.

FIG. 4A illustrates a pair of adjacent micromirrors directing lightbeams towards a substrate, according to some embodiments. In thisexample, a first micromirror 402 and a second micromirror 404 may beconfigured in an “on” position to direct light towards a substrate 451during a digital lithography process. The angle 424 of the firstmicromirror 402 may be at an ideal position, such as +12.0°. The angle426 of the second micromirror 404 may be the same as the angle 424 ofthe first micromirror 402. When these two angles 424, 426 of adjacentmicromirrors 402, 404 are equal to the ideal value, the light beamsreflected from the micromirrors 402, 404 may be reflected directly ontothe substrate 451 at a 90° angle to the substrate 451. For example, afirst light beam 406 projected from a light source may be reflected offthe first micromirror 402 onto the substrate 451 perpendicularly.Similarly, a second light beam 408 may also be reflected off the secondmicromirror 404 onto the substrate 451 perpendicularly. When the lightbeams hit the substrate 451 perpendicularly, this results in verticalfeatures and accurate layouts on the substrate 451.

In addition to ensuring that the light beams are directedperpendicularly onto the substrate 451, another key consideration is theoptical path difference (OPD) 420 between any two adjacent micromirrors.As illustrated in FIG. 4 , the OPD 420 between the first light beam 406and the second light beam 408 represents a difference in the totaldistance traveled by these light beams. Specifically, it may be assumedthat the distance between each of the micromirrors 402, 404 and thesubstrate 451 is the same. However, the distance from the lightsource(s) generating the light beams 406, 408 is different because thesecond micromirror is farther away from the light source(s) than thefirst micromirror. This difference is represented by the OPD 420, andthis OPD 420 results in a phase shift between the first light beam 406and the second light beam 408 on the substrate 451.

FIG. 5 illustrates how an OPD 506 between two adjacent micromirrors mayresult in a phase shift on the substrate, according to some embodiments.A wave representation 502 of a light beam is represented as a sinusoidalwaveform having a wavelength 504. The OPD 506 represents the additionaldistance traveled by the second light beam 408 in FIG. 4A. Assuming thatthe first light beam 406 and the second light beam 408 are in phase whenthe first light beam 406 is reflected off the first micromirror 402, thephase shift 508 may be determined by identifying the remainder whendividing the OPD 506 by the wavelength 504. Each wavelength 504represents a full 3600 phase shift (which can be ignored), and theremainder therefore represents the phase shift between the first lightbeam 406 and the second light beam 408 on the surface of the substrate451. As described in greater detail below, a phase shift that can beaccurately predicted or selected may offer a number of benefits inlithography processes.

FIG. 4B illustrates adjacent micromirrors where the tilt angle isdifferent from an ideal tilt angle, according to some embodiments. WhileFIG. 4A illustrated micromirrors that exhibited tilt angles 424, 426that operated in the “on” position to tilt at the precise 12.0° angle,not all manufactured DMD arrays are this precise. Typically, theaccuracy of the tilt angle in manufactured DMD arrays may vary by asmuch as 1.0°. In order to identify manufactured DMD arrays with a highenough degree of accuracy (e.g., 12.0°+0.06°), batches of manufacturedDMD arrays may need to be analyzed to identify which of the manufacturedDMD arrays actually fall within a tighter manufacturing tolerance. Thisgreatly decreases the yield with which manufactured DMD arrays may beused for lithography processes that require a very precise mirror tilt.

FIG. 4B illustrates the result of micromirrors 402, 404 having tiltangles 440, 442 that are not ideal. Assuming that the position of thelight source(s) remain unchanged, the light beams 406 408 may bereflected off of the micromirrors 402, 404 such that the light beams406, 408 are no longer perpendicular to the substrate 451. This mayresult in angled sidewalls as the light beams 406, 408 penetrate thephotoresist layer on the substrate 451 at an angle. Additionally,because layers on the substrate 451 have a non-negligible thickness,horizontal locations where the light beams 406, 408 hit the substrate451 may vary with the depth of the top layer. Therefore, an error in thetilt angles 440, 442 of the micromirrors 402, 404 may cause thereflected light beams 406, 408 to no longer be perpendicular with thesubstrate 451, causing errors in a pattern printed on the substrate 451.

It should be noted that the pitch 422 between the two adjacentmicromirror's 402, 404 may stay relatively constant within or betweenbatches of manufactured DMD arrays. The pitch 422 can be tightlycontrolled during manufacturing to minimize variations in the distancebetween micromirrors in an array.

FIG. 4C illustrates how variations in the tilt angles 440, 442 may beaddressed by changing the angle of the light beams 406, 408, accordingto some embodiments. When a variation in the tilt angles 440, 442 of themicromirrors 402, 404 causes the reflected light beams 406, 408 to nolonger be perpendicular with the substrate 451, the angle at which thelight beams 406, 408 are projected towards the micromirrors 402, 404 maybe adjusted to compensate. For example, the position of the lightsources may be changed relative to the position of the micromirrors 402,404. Changing the position of the light sources may consequently changethe incident angle of the light beams 406, 408 as they are reflected offof the micromirrors 402, 404. As illustrated in FIG. 4C, this positionmay be adjusted until the light beams 406, 408 are reflected such thatthey are again perpendicular to the substrate 451.

While changing the position or angle at which the light sources projectthe light beams 406, 408 may again cause the light beams 406, 408 to beperpendicular to the substrate 451, this may also cause the OPD tochange between the light beams 406, 408. For example, the OPD 444 inFIG. 4C has been shortened relative to the OPD 420 in FIG. 4A and FIG.4B. As described above and illustrated in FIG. 5 , changing the OPD 444may directly affect the phase shift 508 between the light beams 406, 408on the substrate 451.

Different phase shifts may be desired for different purposes duringlithography processes. For example, a 180° phase shift between adjacentmicromirrors may create a null at the boundary line between the twomicromirrors. This allows the lithography pattern to create very denseline-space patterns where the line-plus-space pitch equals the pitchbetween two adjacent micromirrors for resolution enhancement. In anotherexample, a 0° phase shift between adjacent micromirrors may reinforce apattern at the boundary. Other pattern designs may benefit from usingselectable phase shifts, such as 90°, 270°, and/or any other degreephase shift. Therefore, it may be desirable to not only maintain aselected phase shift to compensate for light source location or tiltangle errors, it may also be desirable to select any phase shift basedon the needs of a particular design.

To overcome this technical problem, the embodiments described herein mayadjust the wavelength of the light beams 406, 408 using varioustechniques in order to select or adjust a desired phase shift. Threevariables may affect the phase shift, namely the pitch 422 between themicromirrors 402, 404; the length of the OPD 444; and the wavelength ofthe light beams 406, 408. Because the pitch 422 may be assumed to berelatively constant, and the OPD 444 may vary in order to maintainperpendicular light beams, some embodiments may adjust the wavelength ofthe light beams 406, 408 to achieve or fine-tune a preselected phaseshift. As illustrated in FIG. 5 , adjusting the wavelength 504 for agiven OPD 506 will adjust the phase shift 508 in a way that may bepredicted and calculated.

FIG. 6 illustrates a system 600 for adjusting a phase shift betweenpixels in digital lithography system, according to some embodiments. Thesystem 600 may include an array of micromirrors, including the pair ofmicromirrors illustrated in FIG. 6 , referred to as the firstmicromirror 402 and the second micromirror 404 for purposes ofdistinction only. As described above, these micromirrors 402, 404 may beoriented in an “on” position (e.g., approximately 12°) to direct lightfrom a light source 602 towards a substrate 451 to print a pattern on alayer on the substrate 451, such as photoresist layer.

The system may include a light source 602. The light source 602 mayinclude one or more laser diodes or other light sources configured togenerate light at a preselected frequency. In order to set or adjust thephase shift based on the ODP 444 as described above, the light source602 may be configured to adjust the wavelength of the light duringoperation. Such adjustments may be made by selecting different colors oflaser diodes in the light source to be operational at different times.Some embodiments may make adjustments to the wavelength by adjusting atemperature of the light source 602 to cause the wavelength toincrease/decrease. Some embodiments may include multiple light sourcesthat can be substituted in the place of the light source 602 to generatewavelengths at different frequencies.

Some embodies may include a controller 604. By way of example, FIG. 13described below includes a computer system that may be used as acontroller for operating the light source 602 as part of the lithographysystem. For example, the controller 604 may include one or moremicroprocessors or microcontrollers, along with one or morenon-transitory computer-readable media that store instructions thatcause the microprocessors/microcontrollers to perform operations thatcontrol the frequency, operation, timing, etc., of the light source 602.

Note that only a single light source 602 is illustrated in FIG. 6 . Thisillustration is provided only by way of example and is not meant to belimiting. The light source 602 may be comprised of multiple laser diodesor other light sources. Other light sources may also be present togenerate light for other micromirrors in the array. Furthermore, thelight source 602 may be responsible for generating light that isreflected as the first light beam 406 and/or the second light beam 408.For example, the first light beam 406 and the second light beam 408 mayoriginate from the same light source 602 or from different light sourceswithout limitation.

FIG. 7 illustrates a flowchart 700 of a method for adjusting orselecting a phase shift between pixels in digital lithography systems,according to some embodiments. The method may include projecting a firstlight beam onto a first spatial light modulator pixel (702). Asdescribed above, the first spatial light modulator pixel may include adigital micromirror. The first spatial light modulator pixel may directthe first light beam onto a substrate during a digital lithographyprocess. The method may also include projecting a second light beam ontoa second spatial light modulator pixel (704). The second spatial lightmodulator pixel may also include a digital micromirror or other similardevice, and may similarly direct the second light beam onto thesubstrate during the digital lithography process. The first and secondspatial light modulator pixels may be positioned adjacent to each otherin an array of pixels. The first and second light beams may originatefrom the same or from different light sources, such as laser diodes orlaser diode arrays that are phase-locked.

This method may be used to set or adjust the phase shift between thefirst light beam and the second light beam on the substrate. Forexample, when referring to a “preselected phase shift,” this refers to aphase shift that is specifically selected for a particular lithographyprocess between these particular micromirrors. This may be contrastedwith simply generating a light at a wavelength using micromirrors thatresults in an OPD based on tilt error and carrying out a process withthe resulting phase shift. Instead, the preselected phase shift may bedetermined for the process, and the wavelength of light from the lightsource may be adjusted or selected in order to generate the preselectedphase shift.

Therefore, the method may further include controlling a wavelength ofthe first light beam and a wavelength of the second light beam based onan optical path difference between the first light beam and the secondlight beam (706). The wavelength may be selected or adjusted in order toproduce the preselected phase shift between the first light beam and thesecond light beam on the substrate. The wavelength may be selected basedon the OPD as described above in relation to FIG. 5 . As describedabove, a light source may be configured such that the wavelength oflight generated by the light source is adjustable. This adjustment maybe made by activating different light sources, adjusting the operationof the light sources, adjusting the temperature of light sources,mechanically adjusting the cavity length of the laser sources,electro-acoustically altering the cavity of the light sources,activating or substituting alternate light sources into the lithographysystem, and/or any other method of adjusting or selecting a wavelengthof light to generate the desired phase shift. For example, a firstsubset of the plurality of laser diodes may be configured to generate awavelength that causes a phase shift of 180°. A second subset of theplurality of laser diodes may be configured to generate a wavelengththat causes a phase shift of 0°, while another subset of the laserdiodes may be configured to generate another wavelength, such as 270°,and so forth. These subsets may be activated based on the preselectedwavelength.

It should be appreciated that the specific steps illustrated in FIG. 7provide particular methods of adjusting or selecting a phase shiftbetween pixels in digital lithography systems according to variousembodiments. Other sequences of steps may also be performed according toalternative embodiments. For example, alternative embodiments mayperform the steps outlined above in a different order. Moreover, theindividual steps illustrated in FIG. 7 may include multiple sub-stepsthat may be performed in various sequences as appropriate to theindividual step. Furthermore, additional steps may be added or removeddepending on the particular applications. Many variations,modifications, and alternatives also fall within the scope of thisdisclosure.

One particular method of adjusting the effective wavelength of the lightsource used in the lithography process will now be described. Thismethod involves using a plurality of light sources having differentfrequencies and adjusting the intensity of these light sources togenerate an effect of a phase shift on the substrate.

FIG. 8 illustrates a light source 800 that may be used in lithographysystems, according to some embodiments. This light source 800 isprovided only by way of example and is not meant to be limiting. Otherlight sources having different groupings and configurations of laserdiodes or other similar equipment may be used in its place. This lightsource 800 may include a laser module 802. The laser module 802 mayinclude a plurality of laser diodes. In some embodiments, the laserdiodes may be divided into groups, and the groups may include aplurality of matched laser diodes that are driven by corresponding drivecircuitry. Each of the groups may be populated with a plurality of laserdiodes having a similar wavelength. Note that FIG. 8 illustrates fourgroups of four laser diodes each only by way of a simplified example forthe sake of clarity. As indicated by the ellipses, any number of laserdiodes and groups may be used without limitation.

For the embodiments described below, some of the groups may includelaser diodes configured to emit light at a wavelength that is shorterthan a preselected wavelength, and some of the groups may include laserdiodes configured to emit a light at a wavelength that is longer thanthe preselected wavelength. For example, a first group 808 may be drivenby first drive circuitry 806 and configured to generate light at thehigher wavelength, while a second group 838 may be driven by seconddrive circuitry 833 and configured to generate light at the lowerwavelength.

The system may include a controller 804 configured to control anintensity of the various groups of laser diodes. For example, thecontroller 804 may be implemented using microprocessors,microcontrollers, and/or a computer system as described below in FIG. 13. The controller 804 may cause the intensity of the first group 808 tobe higher than an intensity of the second group 838, or vice versa. Thecontroller 804 may calculate the appropriate intensity for each group inthe laser module 802 as described in detail below.

Each laser diode in the laser module 802 may be coupled to acorresponding optical fiber 814. These optical fibers may be bundledtogether and aimed into a homogenizing rod 816 or other form of lightpipe that scrambles the light into a uniform illumination beam that maybe projected onto the micromirrors in the array. Therefore, each of the“light beams” described above may include multiple components fromdifferent light laser diode groups generating light at differentwavelengths. For example a first light component may be generated by thefirst group 808 of laser diodes at one wavelength, while a second lightcomponent may be generated by a second group 838 of laser diodes atanother wavelength. The output of the homogenizing rod 816 may be light818 that is directed as one or more light beams as described above. Forexample the light 818 may be the source of both the first light beam andthe second light beam in FIGS. 4A-4C and elsewhere in this disclosure.

FIG. 9 illustrates a system 900 for using light beams having multiplewavelengths that bracket a preselected wavelength, according to someembodiments. The system 900 is similar to the systems described above,except that the light source 911 may be configured to generate a firstlight beam 406 having at least two different components. For example, afirst component may be generated using laser diodes that output light ata wavelength that is higher than the preselected wavelength, where thepreselected wavelength corresponds to a desired phase shift between thefirst light beam 406 and the second light beam 408 on the substrate 451.Similarly, the second component may be generated using laser diodes thatoutput light at a wavelength that is lower than the preselectedwavelength. Alternatively, the first component and the second componentmay be characterized based on their corresponding phase shifts relativeto a preselected phase shift. The first component may generate a phaseshift that is greater than a preselected phase shift, and the secondcomponent may generate a phase shift that is less than the preselectedphase shift. These two components 902, 904 may be mixed together to formthe first light beam 406. As described above, the light source 911 mayalso generate the second light beam 408 that is projected onto thesecond micromirror 404, although this is not shown explicitly in FIG. 9. Alternatively, a second light source (not shown) may generate thesecond light beam 408.

The light source 911 may include a controller as described above thatcontrols the intensity of the first component 902 and the intensity ofthe second component 904. It has been discovered that by bracketing thepreselected wavelength or phase shift on the substrate by wavelengths orphase shifts that are higher and lower than the preselected wavelengthor phase shift, the effect of preselected phase shift can beapproximated by the combined light intensity of the two components onthe substrate. Furthermore, by adjusting the relative intensity betweenthe first component 902 and the second component 904, the effectivephase shift can be tuned or adjusted between the phase shift of thefirst component 902 and the phase shift of the second component 904using a weighted combination of the phase shifts.

FIG. 10 illustrates a graph 1000 of the effect of using a light beamwith multiple light components that bracket the preselected phase shift,according to some embodiments. In this example, the preselected phaseshift is selected as 0°. This corresponds to a preselected wavelengththat can be calculated based on the OPD of the particular micromirrorarrays. Therefore, the preselected phase shift and the preselectedwavelength may be used interchangeably, as they are easily derived fromeach other. Curve 1008 illustrates the intensity of the light on thesurface of the substrate. The vertical axis of the graph 1000 representsan intensity of the light on the substrate using a normalize scale ofarbitrary units. The horizontal axis of the graph 1000 represents alocation on the substrate in microns (μm). The 0 μm location correspondsto a center position between the first micromirror and the secondmicromirror that may be adjacent in the array. The pitch between thesetwo micromirrors may be approximately 1.26 μm, which roughly correspondsto the peaks on the curves in the graph 1000. The results of the graph1000 are based on a defocus level of approximately −3 μm.

Because a light source may not be readily available for the preselectedwavelength corresponding to a 0° phase shift, the first component andthe second component may be used simultaneously that have phase shiftsthat are greater than and less than the preselected phase shift. In thisexample, the first component corresponding to curve 1004 represents awavelength generating a phase shift that is approximately 10° less(e.g., 350°) than the 0° phase shift, and the second componentcorresponding to curve 1002 represents a wavelength generating a phaseshift that is approximately 20° greater than the 0° phase shift. Notethat these curves individually are different from the curve 1008corresponding to the preselected wavelength that generates thepreselected 0° phase shift.

However, when the first component and the second component are combinedto form the light beam reflected off of the micromirror, the overalllight intensity on the substrate can be made to approximate the effectof the preselected phase shift of the preselected wavelength. Forexample, the two components can be combined in a linear combination,where the weights assigned to each component correspond to thedifference of their corresponding phase shifts relative to thepreselected phase shift. In this implementation, the weights assigned toeach component make the linear combination of the two components equalto approximately zero. For example, the component having a phase shiftof −10° relative to the preselected 0° phase shift may be multiplied by⅔, while the component having a phase shift of +20° relative to thepreselected 0° phase shift may be multiplied by ⅓, such that the linearcombination of these components is approximately equal to zero. Theseweights may then be used to control the brightness or intensity of eachcomponent. For example, an intensity of the component having the −10°phase shift may be approximately twice the intensity of the componenthaving the +20° phase shift. The intensity of each component may becontrolled dynamically during operation by the controller as describedabove.

The combination of the two components when the intensity of eachcomponent is controlled is shown as curve 1006 in the graph 1000. Notethat curve 1006 for the combined components very closely approximatescurve 1008 corresponding to the ideal phase shift of the preselectedwavelength. This illustrates how the effect of the first component andthe second component can be used to approximate the effect of thepreselected phase shift or wavelength on the substrate by controllingthe intensity of these components.

FIG. 11 illustrates graphs that show how multiple components can be usedto approximate and tune any preselected wavelength, according to someembodiments. Although 0° and 180° have been described above as examplephase shifts, these embodiments may readily be used to generate anyphase shift between any two micromirrors in the array at various defocuslevels. By way of example, graph 1100 illustrates approximating a 0°phase shift at a +3 μm defocus length, graph 1102 illustratesapproximating a 180° phase shift at a 0 μm defocus length, graph 1106illustrates approximating a 90° phase shift at a +3 μm defocus length,and graph 1108 illustrates approximating a 280° phase shift at a 0 μmdefocus length. These graphs illustrate how any phase shift may beapproximated using these techniques.

In these examples, the phase shifts or wavelengths that bracket thepreselected phase shift or preselected wavelength have been selectedsuch that the higher phase shift is approximately 20° greater than thepreselected phase shift, and the lower phase shift is approximately 10°less than the preselected phase shift. While this particular bracketingof the preselected phase shift has been shown to closely approximate theeffect of the preselected phase shift, not all embodiments need to usethese specific values. For example, other embodiments may use phaseshift values for the first component that are between approximately 5°and approximately 10° greater, between approximately 10° andapproximately 15° greater, between approximately 15° and approximately20° greater, between approximately 20° and approximately 25° greater,between approximately 25° and approximately 30° greater, and so forth.Similarly, other embodiments may use phase shift values for the secondcomponent that are between approximately 5° and approximately 10° less,between approximately 10° and approximately 15° less, betweenapproximately 15° and approximately 20° less, between approximately 20°and approximately 25° less, between approximately 25° and approximately30° less, and so forth. Each of these different ranges may be used indifferent combinations without limitation and have different advantagesdepending on the particular lithography pattern, laser diode type,photoresist material, and/or other characteristics of the lithographysystem.

The system described above may use the same mix of wavelengths in thelaser diodes for the DMD as a whole. This allows the system to correctfor an average error in the mirror tilt angle of each DMD. However, someembodiments may additionally correct for individual micromirror tilterrors with in a DMD array itself. For example, individual wavelengthmixes and incident angles may be adjusted across the DMD based on thetilt error of each individual micromirror. These embodiments may varythe light sources, intensities, and light angles to compensate forregional variations in the micromirror tilt angles.

The examples described above illustrate only two components of the lightbeam by way of example. However, other embodiments may use more than twocomponents for the light beam. For example, the preselected phase shiftmay be bracketed by, three, four, five, etc., components having phaseshifts that are greater than and/or less than the predetermined phaseshift. The relative brightness of each of these components may bedetermined using the weighted combination of light components describedabove. Specifically, the weights corresponding to intensity may becalculated such that the weighted combination of phase shift deviationsfrom the preselected phase shift is approximately zero.

FIG. 12 illustrates a flowchart 1200 of a method of selecting oradjusting a phase shift between pixels in digital lithography systems,according to some embodiments. The method may include projecting a firstlight beam onto a first spatial light modulator pixel (1202). Asdescribed above, the first spatial light modulator pixel may include adigital micromirror. The first spatial light modulator pixel may directthe first light beam onto a substrate during a digital lithographyprocess. The method may also include projecting a second light beam ontoa second spatial light modulator pixel (1204). The second spatial lightmodulator pixel may also include a digital micromirror or other similardevice, and may similarly direct the second light beam onto thesubstrate during the digital lithography process. The first and secondspatial light modulator pixels may be positioned adjacent to each otherin an array of pixels. The first and second light beams may originatefrom the same or from different light sources, such as laser diodes orlaser diode arrays.

The first light beam may include a plurality of components including afirst component having a first wavelength that generates a first phaseshift that is greater than a preselected phase shift. Similarly, theplurality of components may also include a second component having asecond wavelength that generates a second phase shift that is less thanthe preselected phase shift. The preselected phase shift may correspondto a desired phase shift between the light beams reflected by twomicromirrors onto the substrate. As described above, the plurality ofcomponents in the first light beam may also include other components inaddition to the two specific components described above. The same lightsource that generates the first light beam may also generate the secondlight beam, and therefore the second light beam may also include thesecomponents.

The method may further include controlling intensities of the pluralityof components to generate an effect on the substrate that approximatesthe preselected phase shift (1206). The intensities of each componentmay be controlled based on a linear combination of deviations of thecorresponding phase shifts from the preselected phase shift. The weightsapplied to each of these phase shift deviations in the weightedcombination may be calculated such that the linear combination isapproximately zero. The weighted combination may include any number ofcomponents in the light beams. Approximating the preselected phase shiftmay generate a pattern of light intensity on the substrate thatapproximates the pattern of light intensity that will be present using asingle wavelength that corresponds to the preselected phase shift.

It should be appreciated that the specific steps illustrated in FIG. 12provide particular methods of selecting or adjusting a phase shiftbetween pixels in a digital lithography systems according to variousembodiments. Other sequences of steps may also be performed according toalternative embodiments. For example, alternative embodiments mayperform the steps outlined above in a different order. Moreover, theindividual steps illustrated in FIG. 12 may include multiple sub-stepsthat may be performed in various sequences as appropriate to theindividual step. Furthermore, additional steps may be added or removeddepending on the particular applications. Many variations,modifications, and alternatives also fall within the scope of thisdisclosure.

Each of the methods described herein may be implemented by a computersystem. Each step of these methods may be executed automatically by thecomputer system, and/or may be provided with inputs/outputs involving auser. For example, a user may provide inputs for each step in a method,and each of these inputs may be in response to a specific outputrequesting such an input, wherein the output is generated by thecomputer system. Each input may be received in response to acorresponding requesting output. Furthermore, inputs may be receivedfrom a user, from another computer system as a data stream, retrievedfrom a memory location, retrieved over a network, requested from a webservice, and/or the like. Likewise, outputs may be provided to a user,to another computer system as a data stream, saved in a memory location,sent over a network, provided to a web service, and/or the like. Inshort, each step of the methods described herein may be performed by acomputer system, and may involve any number of inputs, outputs, and/orrequests to and from the computer system which may or may not involve auser. Those steps not involving a user may be said to be performedautomatically by the computer system without human intervention.Therefore, it will be understood in light of this disclosure, that eachstep of each method described herein may be altered to include an inputand output to and from a user, or may be done automatically by acomputer system without human intervention where any determinations aremade by a processor. Furthermore, some embodiments of each of themethods described herein may be implemented as a set of instructionsstored on a tangible, non-transitory storage medium to form a tangiblesoftware product.

FIG. 13 illustrates an exemplary computer system 1300, in which variousembodiments may be implemented. The system 1300 may be used to implementany of the computer systems or controllers described above. For example,the system 1300 may be used to implement a controller that controls theintensities of the components of the light projected onto themicromirrors and reflected onto the substrate during the lithographyprocesses described above. As shown in the figure, computer system 1300includes a processing unit 1304 that communicates with a number ofperipheral subsystems via a bus subsystem 1302. These peripheralsubsystems may include a processing acceleration unit 1306, an I/Osubsystem 1308, a storage subsystem 1318 and a communications subsystem1324. Storage subsystem 1318 includes tangible computer-readable storagemedia 1322 and a system memory 1310.

Bus subsystem 1302 provides a mechanism for letting the variouscomponents and subsystems of computer system 1300 communicate with eachother as intended. Although bus subsystem 1302 is shown schematically asa single bus, alternative embodiments of the bus subsystem may utilizemultiple buses. Bus subsystem 1302 may be any of several types of busstructures including a memory bus or memory controller, a peripheralbus, and a local bus using any of a variety of bus architectures. Forexample, such architectures may include an Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnect (PCI) bus, which can beimplemented as a Mezzanine bus manufactured to the IEEE P1386.1standard.

Processing unit 1304, which can be implemented as one or more integratedcircuits (e.g., a conventional microprocessor or microcontroller),controls the operation of computer system 1300. One or more processorsmay be included in processing unit 1304. These processors may includesingle core or multicore processors. In certain embodiments, processingunit 1304 may be implemented as one or more independent processing units1332 and/or 1334 with single or multicore processors included in eachprocessing unit. In other embodiments, processing unit 1304 may also beimplemented as a quad-core processing unit formed by integrating twodual-core processors into a single chip.

In various embodiments, processing unit 1304 can execute a variety ofprograms in response to program code and can maintain multipleconcurrently executing programs or processes. At any given time, some orall of the program code to be executed can be resident in processor(s)1304 and/or in storage subsystem 1318. Through suitable programming,processor(s) 1304 can provide various functionalities described above.Computer system 1300 may additionally include a processing accelerationunit 1306, which can include a digital signal processor (DSP), aspecial-purpose processor, and/or the like.

I/O subsystem 1308 may include user interface input devices and userinterface output devices. User interface input devices may include akeyboard, pointing devices such as a mouse or trackball, a touchpad ortouch screen incorporated into a display, a scroll wheel, a click wheel,a dial, a button, a switch, a keypad, audio input devices with voicecommand recognition systems, microphones, and other types of inputdevices. User interface input devices may include, for example, motionsensing and/or gesture recognition devices such as the Microsoft Kinect®motion sensor that enables users to control and interact with an inputdevice, such as the Microsoft Xbox® 360 game controller, through anatural user interface using gestures and spoken commands. Userinterface input devices may also include eye gesture recognition devicessuch as the Google Glass® blink detector that detects eye activity(e.g., ‘blinking’ while taking pictures and/or making a menu selection)from users and transforms the eye gestures as input into an input device(e.g., Google Glass®). Additionally, user interface input devices mayinclude voice recognition sensing devices that enable users to interactwith voice recognition systems (e.g., Siri® navigator), through voicecommands.

User interface input devices may also include, without limitation, threedimensional (3D) mice, joysticks or pointing sticks, gamepads andgraphic tablets, and audio/visual devices such as speakers, digitalcameras, digital camcorders, portable media players, webcams, imagescanners, fingerprint scanners, barcode reader 3D scanners, 3D printers,laser rangefinders, and eye gaze tracking devices. Additionally, userinterface input devices may include, for example, medical imaging inputdevices such as computed tomography, magnetic resonance imaging,positron emission tomography, medical ultrasonography devices. Userinterface input devices may also include, for example, audio inputdevices such as MIDI keyboards, digital musical instruments and thelike.

User interface output devices may include a display subsystem, indicatorlights, or non-visual displays such as audio output devices, etc. Thedisplay subsystem may be a cathode ray tube (CRT), a flat-panel device,such as that using a liquid crystal display (LCD) or plasma display, aprojection device, a touch screen, and the like. In general, use of theterm “output device” is intended to include all possible types ofdevices and mechanisms for outputting information from computer system1300 to a user or other computer. For example, user interface outputdevices may include, without limitation, a variety of display devicesthat visually convey text, graphics and audio/video information such asmonitors, printers, speakers, headphones, automotive navigation systems,plotters, voice output devices, and modems.

Computer system 1300 may comprise a storage subsystem 1318 thatcomprises software elements, shown as being currently located within asystem memory 1310. System memory 1310 may store program instructionsthat are loadable and executable on processing unit 1304, as well asdata generated during the execution of these programs.

Depending on the configuration and type of computer system 1300, systemmemory 1310 may be volatile (such as random access memory (RAM)) and/ornon-volatile (such as read-only memory (ROM), flash memory, etc.) TheRAM typically contains data and/or program modules that are immediatelyaccessible to and/or presently being operated and executed by processingunit 1304. In some implementations, system memory 1310 may includemultiple different types of memory, such as static random access memory(SRAM) or dynamic random access memory (DRAM). In some implementations,a basic input/output system (BIOS), containing the basic routines thathelp to transfer information between elements within computer system1300, such as during start-up, may typically be stored in the ROM. Byway of example, and not limitation, system memory 1310 also illustratesapplication programs 1312, which may include client applications, Webbrowsers, mid-tier applications, relational database management systems(RDBMS), etc., program data 1314, and an operating system 1316. By wayof example, operating system 1316 may include various versions ofMicrosoft Windows®, Apple Macintosh®, and/or Linux operating systems, avariety of commercially-available UNIX® or UNIX-like operating systems(including without limitation the variety of GNU/Linux operatingsystems, the Google Chrome® OS, and the like) and/or mobile operatingsystems such as iOS, Windows® Phone, Android® OS, BlackBerry® 10 OS, andPalm® OS operating systems.

Storage subsystem 1318 may also provide a tangible computer-readablestorage medium for storing the basic programming and data constructsthat provide the functionality of some embodiments. Software (programs,code modules, instructions) that when executed by a processor providethe functionality described above may be stored in storage subsystem1318. These software modules or instructions may be executed byprocessing unit 1304. Storage subsystem 1318 may also provide arepository for storing data used in accordance with some embodiments.

Storage subsystem 1300 may also include a computer-readable storagemedia reader 1320 that can further be connected to computer-readablestorage media 1322. Together and, optionally, in combination with systemmemory 1310, computer-readable storage media 1322 may comprehensivelyrepresent remote, local, fixed, and/or removable storage devices plusstorage media for temporarily and/or more permanently containing,storing, transmitting, and retrieving computer-readable information.

Computer-readable storage media 1322 containing code, or portions ofcode, can also include any appropriate media, including storage mediaand communication media, such as but not limited to, volatile andnon-volatile, removable and non-removable media implemented in anymethod or technology for storage and/or transmission of information.This can include tangible computer-readable storage media such as RAM,ROM, electronically erasable programmable ROM (EEPROM), flash memory orother memory technology, CD-ROM, digital versatile disk (DVD), or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or other tangible computerreadable media. This can also include nontangible computer-readablemedia, such as data signals, data transmissions, or any other mediumwhich can be used to transmit the desired information and which can beaccessed by computing system 1300.

By way of example, computer-readable storage media 1322 may include ahard disk drive that reads from or writes to non-removable, nonvolatilemagnetic media, a magnetic disk drive that reads from or writes to aremovable, nonvolatile magnetic disk, and an optical disk drive thatreads from or writes to a removable, nonvolatile optical disk such as aCD ROM, DVD, and Blu-Ray® disk, or other optical media.Computer-readable storage media 1322 may include, but is not limited to,Zip® drives, flash memory cards, universal serial bus (USB) flashdrives, secure digital (SD) cards, DVD disks, digital video tape, andthe like. Computer-readable storage media 1322 may also include,solid-state drives (SSD) based on non-volatile memory such asflash-memory based SSDs, enterprise flash drives, solid state ROM, andthe like, SSDs based on volatile memory such as solid state RAM, dynamicRAM, static RAM, DRAM-based SSDs, magnetoresistive RAM (MRAM) SSDs, andhybrid SSDs that use a combination of DRAM and flash memory based SSDs.The disk drives and their associated computer-readable media may providenon-volatile storage of computer-readable instructions, data structures,program modules, and other data for computer system 1300.

Communications subsystem 1324 provides an interface to other computersystems and networks. Communications subsystem 1324 serves as aninterface for receiving data from and transmitting data to other systemsfrom computer system 1300. For example, communications subsystem 1324may enable computer system 1300 to connect to one or more devices viathe Internet. In some embodiments communications subsystem 1324 caninclude radio frequency (RF) transceiver components for accessingwireless voice and/or data networks (e.g., using cellular telephonetechnology, advanced data network technology, such as 3G, 4G or EDGE(enhanced data rates for global evolution), WiFi (IEEE 802.11 familystandards, or other mobile communication technologies, or anycombination thereof), global positioning system (GPS) receivercomponents, and/or other components. In some embodiments communicationssubsystem 1324 can provide wired network connectivity (e.g., Ethernet)in addition to or instead of a wireless interface.

In some embodiments, communications subsystem 1324 may also receiveinput communication in the form of structured and/or unstructured datafeeds 1326, event streams 1328, event updates 1330, and the like onbehalf of one or more users who may use computer system 1300.

By way of example, communications subsystem 1324 may be configured toreceive data feeds 1326 in real-time from users of social networksand/or other communication services such as Twitter® feeds, Facebook®updates, web feeds such as Rich Site Summary (RSS) feeds, and/orreal-time updates from one or more third party information sources.

Additionally, communications subsystem 1324 may also be configured toreceive data in the form of continuous data streams, which may includeevent streams 1328 of real-time events and/or event updates 1330, thatmay be continuous or unbounded in nature with no explicit end. Examplesof applications that generate continuous data may include, for example,sensor data applications, financial tickers, network performancemeasuring tools (e.g. network monitoring and traffic managementapplications), clickstream analysis tools, automobile trafficmonitoring, and the like.

Communications subsystem 1324 may also be configured to output thestructured and/or unstructured data feeds 1326, event streams 1328,event updates 1330, and the like to one or more databases that may be incommunication with one or more streaming data source computers coupledto computer system 1300.

Computer system 1300 can be one of various types, including a handheldportable device (e.g., an iPhone® cellular phone, an iPad® computingtablet, a PDA), a wearable device (e.g., a Google Glass® head mounteddisplay), a PC, a workstation, a mainframe, a kiosk, a server rack, orany other data processing system.

Due to the ever-changing nature of computers and networks, thedescription of computer system 1300 depicted in the figure is intendedonly as a specific example. Many other configurations having more orfewer components than the system depicted in the figure are possible.For example, customized hardware might also be used and/or particularelements might be implemented in hardware, firmware, software (includingapplets), or a combination. Further, connection to other computingdevices, such as network input/output devices, may be employed. Based onthe disclosure and teachings provided herein, other ways and/or methodsto implement the various embodiments should be apparent.

As used herein, the terms “about” or “approximately” or “substantially”may be interpreted as being within a range that would be expected by onehaving ordinary skill in the art in light of the specification.

In the foregoing description, for the purposes of explanation, numerousspecific details were set forth in order to provide a thoroughunderstanding of various embodiments. It will be apparent, however, thatsome embodiments may be practiced without some of these specificdetails. In other instances, well-known structures and devices are shownin block diagram form.

The foregoing description provides exemplary embodiments only, and isnot intended to limit the scope, applicability, or configuration of thedisclosure. Rather, the foregoing description of various embodimentswill provide an enabling disclosure for implementing at least oneembodiment. It should be understood that various changes may be made inthe function and arrangement of elements without departing from thespirit and scope of some embodiments as set forth in the appendedclaims.

Specific details are given in the foregoing description to provide athorough understanding of the embodiments. However, it will beunderstood that the embodiments may be practiced without these specificdetails. For example, circuits, systems, networks, processes, and othercomponents may have been shown as components in block diagram form inorder not to obscure the embodiments in unnecessary detail. In otherinstances, well-known circuits, processes, algorithms, structures, andtechniques may have been shown without unnecessary detail in order toavoid obscuring the embodiments.

Also, it is noted that individual embodiments may have been described asa process which is depicted as a flowchart, a flow diagram, a data flowdiagram, a structure diagram, or a block diagram. Although a flowchartmay have described the operations as a sequential process, many of theoperations can be performed in parallel or concurrently. In addition,the order of the operations may be re-arranged. A process is terminatedwhen its operations are completed, but could have additional steps notincluded in a figure. A process may correspond to a method, a function,a procedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination can correspond to a return of thefunction to the calling function or the main function.

The term “computer-readable medium” includes, but is not limited toportable or fixed storage devices, optical storage devices, wirelesschannels and various other mediums capable of storing, containing, orcarrying instruction(s) and/or data. A code segment ormachine-executable instructions may represent a procedure, a function, asubprogram, a program, a routine, a subroutine, a module, a softwarepackage, a class, or any combination of instructions, data structures,or program statements. A code segment may be coupled to another codesegment or a hardware circuit by passing and/or receiving information,data, arguments, parameters, or memory contents. Information, arguments,parameters, data, etc., may be passed, forwarded, or transmitted via anysuitable means including memory sharing, message passing, token passing,network transmission, etc.

Furthermore, embodiments may be implemented by hardware, software,firmware, middleware, microcode, hardware description languages, or anycombination thereof. When implemented in software, firmware, middlewareor microcode, the program code or code segments to perform the necessarytasks may be stored in a machine readable medium. A processor(s) mayperform the necessary tasks.

In the foregoing specification, features are described with reference tospecific embodiments thereof, but it should be recognized that not allembodiments are limited thereto. Various features and aspects of someembodiments may be used individually or jointly. Further, embodimentscan be utilized in any number of environments and applications beyondthose described herein without departing from the broader spirit andscope of the specification. The specification and drawings are,accordingly, to be regarded as illustrative rather than restrictive.

Additionally, for the purposes of illustration, methods were describedin a particular order. It should be appreciated that in alternateembodiments, the methods may be performed in a different order than thatdescribed. It should also be appreciated that the methods describedabove may be performed by hardware components or may be embodied insequences of machine-executable instructions, which may be used to causea machine, such as a general-purpose or special-purpose processor orlogic circuits programmed with the instructions to perform the methods.These machine-executable instructions may be stored on one or moremachine readable mediums, such as CD-ROMs or other type of opticaldisks, floppy diskettes, ROMs, RAMs, EPROMs, EEPROMs, magnetic oroptical cards, flash memory, or other types of machine-readable mediumssuitable for storing electronic instructions. Alternatively, the methodsmay be performed by a combination of hardware and software.

1. A digital lithography system comprising: a first spatial lightmodulator pixel configured to direct a first light beam onto a substrateduring a digital lithography process; a second spatial light modulatorpixel configured to direct a second light beam onto the substrate duringthe digital lithography process; a light source configured to generatethe first light beam, wherein the first light beam comprises a pluralityof components comprising: a first component having a first wavelengththat generates a first phase shift that is greater than a preselectedphase shift; and a second component having a second wavelength thatgenerates a second phase shift that is less than the preselected phaseshift; and a controller configured to control intensities of theplurality of components to generate an effect on the substrate thatapproximates the preselected phase shift.
 2. The system of claim 1,wherein the second spatial light modulator pixel is adjacent to thefirst spatial light modulator pixel in an array of spatial lightmodulator pixels in a digital micromirror device.
 3. The system of claim1, wherein the first spatial light modulator pixel comprises amicromirror that adjusts between an on position that reflects light ontothe substrate and an off position that reflects light away from thesubstrate.
 4. The system of claim 1, wherein the light source is alsoconfigured to generate the second light beam, such that the first lightbeam and the second light beam originate from the light source.
 5. Thesystem of claim 1, wherein the second light beam is generated from adifferent light source, and the controller is further configured tocontrol intensities of components in the second light beam to correctfor a tilt error in the second spatial light modulator pixel that isdifferent from a tilt error in the first spatial light modulator pixel.6. The system of claim 1, wherein the light source comprises a pluralityof groups of laser diodes, wherein a first subset of the plurality ofgroups of laser diodes is configured to output approximately the firstwavelength, and a second subset of the plurality of groups of laserdiodes is configured to output approximately the second wavelength. 7.The system of claim 1, wherein the light source comprises a homogenizingrod that mixes the first component together with the second component togenerate a uniform first light beam.
 8. The system of claim 1, whereinthe plurality of components comprises a plurality of additionalcomponents in addition to the first component and the second component.9. A method of adjusting a phase shift between pixels in digitallithography systems, the method comprising: projecting a first lightbeam onto a first spatial light modulator pixel, wherein the firstspatial light modulator pixel directs the first light beam onto asubstrate during a digital lithography process, wherein the first lightbeam comprises a plurality of components comprising: a first componenthaving a first wavelength that generates a first phase shift that isgreater than a preselected phase shift; and a second component having asecond wavelength that generates a second phase shift that is less thanthe preselected phase shift; projecting a second light beam onto asecond spatial light modulator pixel, wherein the second spatial lightmodulator pixel directs the second light beam onto the substrate duringthe digital lithography process; and controlling intensities of theplurality of components to generate an effect on the substrate thatapproximates the preselected phase shift.
 10. The method of claim 9,wherein the first wavelength generates a first phase shift that isapproximately 20° greater than the preselected phase shift.
 11. Themethod of claim 9, wherein the second wavelength generates a secondphase shift that is approximately 10° less than the preselected phaseshift.
 12. The method of claim 9, wherein the preselected phase shift isselectable to be any phase shift between 0° and 359°.
 13. The method ofclaim 9, wherein controlling the intensities of the plurality ofcomponents comprises calculating weights for each of the plurality ofcomponents in a linear combination of the deviations between the firstphase shift and the second phase shift from the preselected phase shiftsuch that the linear combination is approximately zero.
 14. The methodof claim 13, wherein the weights in the linear combination correspond tothe intensities of the plurality of components.
 15. The method of claim9, wherein approximating the preselected phase shift generates a patternof light intensity on the substrate that approximates a pattern of lightintensity that would be present on the substrate using a singlewavelength corresponding to the preselected phase shift.
 16. The methodof claim 9, wherein the first phase shift is calculated from the firstwavelength and an optical path difference between the first light beamon the second light beam.
 17. The method of claim 9, wherein the secondspatial light modulator pixel is adjacent to the first spatial lightmodulator pixel in an array of spatial light modulator pixels in adigital micromirror device, and the second light beam also comprises thefirst component and the second component.
 18. A method of adjusting orselecting a phase shift between pixels in digital lithography systems,the method comprising: projecting a first light beam onto a firstspatial light modulator pixel, wherein the first spatial light modulatorpixel directs the first light beam onto a substrate during a digitallithography process; projecting a second light beam onto a secondspatial light modulator pixel, wherein the second spatial lightmodulator pixel directs the second light beam onto the substrate duringthe digital lithography process, and the second spatial light modulatorpixel is adjacent to the first spatial light modulator pixel in an arrayof spatial light modulator pixels; and controlling a wavelength of thefirst light beam and/or a wavelength of the second light beam based onan optical path difference between the first light beam and the secondlight beam to produce a preselected phase shift between the first lightbeam and the second light beam on the substrate.
 19. The method of claim18, wherein controlling the wavelength of the first light beam comprisesswitching between different laser diodes that generate light havingdifferent wavelengths.
 20. The method of claim 18, wherein controllingthe wavelength of the first light beam comprises changing the wavelengthof the first light beam by controlling a temperature of a light source,mechanically altering a cavity of the light source, orelectro-acoustically altering the cavity of the light source.